The embodiment relates to a light emitting device, a method of manufacturing the same, a light emitting device package, and a lighting system.
An LED (light emitting device) is an element that converts electric energy into a light energy. For instance, the LED can produce various colors by adjusting the compositional ratio of compound semiconductors.
The LED based on nitride semiconductor thin films is advantageous as compared with conventional light sources, such as a fluorescent lamp or a glow lamp, in terms of power consumption, life span, response speed, safety and environmental-friendly requirement. Thus, application of the LED has been expanded to the extent of an LED backlight that may substitute for a cold cathode fluorescence lamp (CCFL) constituting a backlight of a liquid crystal display (LCD), a white LED lighting device that may substitute for a fluorescent lamp or a glow lamp, a headlight of a vehicle and a signal lamp.
As the application of the nitride semiconductor LED has been expanded, it is necessary to develop the LED having the high power and high efficiency.
Meanwhile, according to a nitride semiconductor LED including an active layer having a multi-quantum well structure of the related art, quantum wells in the active layer may not uniformly distribute carriers injected thereto, so only few quantum wells adjacent to a hole injection layer may contribute to the light emission. Thus, if a great amount of current is injected, extra electrons, which are not effectively confined in the active layer, may be generated.
These extra electrons do not contribute to the light emission, but may be extinguished in the active layer or leaked out of the active layer.
In addition, according to the related art, the recombination of the electron-hole is mainly carried out in the last quantum well adjacent to the hole injection layer. Since the last quantum well has the low light emitting efficiency, the light emitting efficiency of the LED may be lowered.